firmament

American  

[fur-muh-muhnt] / ˈfɜr mə mənt /

noun

1. the vault of heaven; sky.

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firmament British  

/ ˈfɜːməmənt, ˌfɜːməˈmɛntəl /

noun

1. the expanse of the sky; heavens

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Other Word Forms

• firmamental adjective

Etymology

Origin of firmament

1250–1300; Middle English < Late Latin firmāmentum sky, Latin: support, prop, stay, equivalent to firmā ( re ) to strengthen, support ( see firm ²) + -mentum -ment

Explanation

The firmament is the curve of the sky, especially if you imagine it as a solid surface. You can describe the sky at night as a firmament shining with stars (if you're feeling poetic). The word firmament comes from the Latin firmus, or "firm," and this description of the sky as something solid reflects ancient ideas of the way the universe was constructed. The first stargazers imagined the sky as a sphere, and it wasn't until the late 1500s that the idea of an infinite universe was seriously considered. Today the word firmament is mostly literary, used to poetically describe the visual curve of the sky.

Example Sentences

Let’s take a moment to appreciate the cabin headliner, twinkling like thousands of LED stars in the firmament.

From The Wall Street Journal • Apr. 4, 2026

Today our stars inhabit the cultural firmament, in sports and in entertainment.

From The Wall Street Journal • Dec. 18, 2025

Time and cultural amnesia restored all these stars to the firmament of our good graces, as I’m sure will happen with most of these comedians.

From Salon • Oct. 5, 2025

Of course, long before audiences became obsessed with Brody’s turn as a hot rabbi in “Nobody Wants This,” both he and Meester were cemented in the pop culture firmament as teen drama icons.

From Los Angeles Times • May 1, 2025

If so, she would surely go down in the history books as a hero to all in the theatrical firmament.

From "The Long-Lost Home" by Maryrose Wood